The cable television industry is not a unified one. It has evolved from a large number of independent providers and a larger number of vendors who supply them with equipment. This has resulted in the use of a large number of equipment and cable standards throughout the industry. The situation is further complicated by the range of environments in which transmission cables and equipment must operate. The requirements for a central office to distribution hub connection, for example, are significantly different than those for the connection from the street to a subscribers house. Other industries reflect a similar growth and exhibit their own version of the following problems.
One direct consequence of this environment is the range of coaxial cable sizes in use and the range of receptacle sizes in use on the equipment to which the cables connect. Common sizes for center conductors range from 0.023" through 0.25". Outer conductors exhibit a similar range. Where a cable of a certain size is to be connected to an equipment receptacle of the same size, a simple pass through connector can be used. This type of connector grips the outer conductor and possibly the insulation of the cable and then threads into (or connect in some other manner) the receptacle, providing a physical connection as well as the electrical connection for the outer conductor. The center conductor extends through the connector and mates with a corresponding contact on the equipment receptacle. When the connector is separated from the equipment receptacle, the center conductor of the cable typically passes completely through the connector and protrudes beyond it, giving rise to the name "pass through" connector.
It is frequently necessary to connect a cable to a piece of equipment where the conductor size and the receptacle size is mismatched. A common situation for this is where cable designed for a long exterior run, such as a distribution cable from a central office, is routed into a building and connected to equipment designed for interior use and for connection to local cable runs. The presents the common problem of connecting a cable with a larger center conductor to a receptacle designed to receive a smaller conductor. The prior art approach to solving this problem is to use a reducing, or "pin type", connector similar to that pictured in FIG. 12. The connector, 230, is a multi-part assembly which attaches to the cable and connects the center conductor to a pin, 236, which is then used to connect to the equipment. A typical example of such a connector requires 14 separate parts and 4 o-rings to make the connection. Several of these parts are necessitated solely by the need to retain and position the pin. The connector also introduces an additional connection at the conductor to pin interface. Each connection can be a source of problems including RF noise, and unnecessary connections are undesirable. In addition, several impedance changes occur within the connector as the relative diameters of the center conductor (or pin) and the connector cavity change.
Impedance is a critical measurement of the effective resistance a coaxial connection and is directly related to the ratio of the outer diameter (OD) of the center conductor and the inner diameter (ID) of the enclosing outer conductor or connector housing, as is well known in the art. Changes in impedance along the path through a connector cause RF noise and signal degradation. To reduce impedance changes, changes in the conductor OD (such as at the connector to pin connection) should be matched with a change in the ID of connector and there should be no changes in connector ID not matched by connector OD changes. (This is a slight simplification because changes in the dielectric material within the gap between the center and outer conductors also impacts the impedance.) As can be seen in FIG. 12, there are several points where there is a mismatched change in one of the diameters leading to a degradation in the signal.
The reduction connector is significantly more complex and more expensive than the pass through connector. The price difference, even where purchased in large quantities is estimated at $1.00 per connector. Given the hundreds of thousands, or even millions, of connectors required by a cable company, this is a significant expense. In addition, a company needs to maintain an inventory of all of the various connector sizes required to address all of the possible size changes encountered throughout its system.
There is a need for a tool which reduces the diameter of the center conductor of a coaxial cable to the size necessary to mate directly with a smaller size receptacle, allowing a pass through connector to be used in place of a reducing connector. Because of the various combinations of connector and cable sizes encountered, the tool should be able to reduce a range of original center conductor sizes to the same reduced size. The tool should be readily adapted to produce different reduced sizes. The tool should be easy to use and be usable in typical field conditions encountered by those in the cable television and other communications industries. The tool should provide precise control over the profile of the reduction in the conductor and over the placement of that profile relative to some point on the cable, such as the end of the outer conductor, to allow precise alignment of the reduction profile with matching profiles in the connector.